The invention relates to a packaging system for the in-situ preparation of cosmetic formulations which has a micromixer. This micromixer may be connected to one or more stock chambers.
Cosmetic formulations are frequently prepared using simple stirred vessels with various types of stirrer. Depending on the stirrer type (for example anchor, propeller, inclined-blade, disc or EKATO multistage impulse countercurrent stirrers or EKATO Mizer disc), different shear forces occur in the stirred vessels. Temperature distribution and also the energy input into the formulation are affected by the stirrer. the shear forces, temperature and introduced energy are not uniformly distributed in the batch vessel and thus affect the build-up of the resultant formulation.
Cosmetic formulations are usually commercially available in the form of packaged creams, emulsions, lotions and gels. In this connection, the shelf life and the stability of the formulations represents a problem. For this reason, the products contain a wide variety of additives, which may result in irritation or allergic reactions in the case of very sensitive users. In various cases, stability reasons also mean that it may not be the actual active ingredients that are employed in the formulations, but instead suitable derivatives have to be used which only decompose at the site of action. The latter is associated firstly with a time delay and with the effect or liberation of a further compound. Both together may significantly reduce the effectiveness of the actual active ingredients.
In order to circumvent these problems, various systems have been developed in which formulations are stored separately in different vessels or stock chambers. The separate formulations are not mixed until directly before use, either by combining the formulations from the different stock chambers and mixing them with one another by shaking or stirring. In some cases, the formulations have to be manually mixed with one another in advance. Another possibility is to combine the separate formulations from the stock vessels via channels or thin tubes in an output aperture by means of a pump system connected to one another.
These systems all have the disadvantage that only restricted mixing of the initially introduced formulations is possible and the formation of high-quality emulsions is not possible by mixing taking place in this way, in particular of microemulsions, unless an initially introduced emulsion is only mixed with an active ingredient-containing formulation.
The object of the present invention is therefore to provide a packaging system by means of which high-quality creams, emulsions, lotions, gels or other cosmetic formulations can be prepared in situ in a simple manner by the user. A further object of the invention is to provide a packaging system by means of which the use of various additives, such as emulsifiers, surfactants, preservatives and the like, which can act as irritants or cause allergic reactions for sensitive persons, can be reduced or entirely avoided.
The object is achieved by a packaging system for the in-situ preparation of cosmetic formulations which has a micromixer.
The present invention therefore relates to a packaging system of this type which has one, in particular two or more, stock chambers, each of which is provided with a thin tube, each of which terminates in a channel of a micromixer, in which mixing of the flowable components present from the various stock chambers can take place.
The various stock chambers advantageously have a common pump system. The stock chambers may be under pressure.
The stock chambers may, for the purposes of use, be connectable to the pump system, which is connected to a micromixer and has a dispensing aperture for the mixed product.
The present invention also relates to a corresponding packaging system which has two or more stock chambers connected externally to one another.
In accordance with the invention, a constituent of the packaging system is a micromixer consisting of two or more thin sheet-like structures which are connected permanently to one another and which have repeatedly crossing channels in at least one of the surfaces facing one another.
This micromixer can be made of metal, silicon or plastic structures.
In a particular embodiment, the packaging system may be designed in such a way that the pump system, which is connected to a micromixer and has an dispensing aperture for the mixed product, is re-usable.
The present invention relates to a packaging system for the in-situ preparation of cosmetic formulations in the form of lotions, emulsions, gels or creams or of liposome-containing or active ingredient-containing formulations.
For certain formulations, uniform mixing, temperature and energy input, even at the micro-level, is important. A micromixer enables preparation under uniform temperature conditions at the micro-level. In contrast to a large-volume stirred reactor, the energy input is the same in the very small volumes for all contents. Furthermore, microemulsions can be prepared better via the multiple shear conditions of the communicating channels than in a stirred vessel. The micromixer is suitable for the preparation of very fine and homogeneous formulations.
It has now been found that the use of micromixers enables the in-situ preparation of mixtures in the form of emulsions, suspensions and dispersions, lotions, solutions, gels and creams in which all contents are uniformly distributed, even in extremely small volume parts.
It is possible to prepare these mixtures under uniform temperature conditions at the micro-level, since as good as no temperature gradient forms in the thin, optionally laminate-like channels owing to the small volumes if the separately introduced formulations are warmed. Furthermore, the input of energy is the same in each volume part, i.e. even in the smallest. It has also been found that emulsions having a significantly more homogeneous droplet size distribution can be prepared than in a stirred vessel. Owing to the multiple shear conditions of the communicating channels in the micromixer, droplet sizes in the micro-range are inevitably specified, so that microemulsions are obtained, which could only be prepared in a very complex manner in a stirred vessel. The use of a micromixer is therefore suitable for the preparation of very fine homogeneous formulations. This is advantageously possible in situ.
Suitable for the packaging system according to the invention are micromixers and associated connection and sealing systems which are described in the patent applications DE 1 95 11 603, DE 1 97 46 583, DE 1 97 46 584, DE 19746585 and DE 1 98 54 096, and modifications thereof that are evident to the person skilled in the art. Suitable micromixers and associated connection and sealing systems may consist of suitable metallic, ceramic or polymeric materials or of silicon. They can be mechanically connected or adhesively bonded. The connection to the other parts of the packaging system according to the invention is preferably effected mechanically. It goes without saying here that pressurised parts are undetachably connected to sealing parts. This means that the present invention includes both packaging systems whose stock chambers are under pressure and are provided with withdrawal valves and unpressurised packaging systems from which the formulations are withdrawn with the aid of pump systems.
Problematic formulations in the W/O area are emulsions, in particular those having high contents of vegetable triglycerides. Emulsions without stabilising waxes are frequently distinguished by inadequate long-term viscosity constancy, and O/W lotions are generally more difficult to stabilise than creams. These emulsions can therefore be prepared particularly well using micromixers. It is of particular advantage here than the use of micromixers enables particularly small amounts to be prepared, which can advantageously be prepared in situ, i.e. directly before use.
Microemulsions are thermodynamically stable if, owing to extremely low interfacial energy, they are formed spontaneously, i.e. without the supply of external mechanical energy. The droplet diameters are significantly smaller than in the case of microemulsions; they are in the range 10-30 nm (nanometers), i.e. below the wavelength of visible light. Microemulsions are therefore colloidally disperse, optically transparent systems. According to POHLER, certain concentration ranges of the oil and water phases and of the emulsifiers and auxiliaries must be observed for the formulation of microemulsions:
The use of micromixers for the preparation of microemulsions enables the use of surfactants to be considerably reduced, enabling the toleration for particularly sensitive skin types to be significantly increased. Stable microemulsions can be prepared using as little as less than 10% by weight of surfactants. In certain formulations, surfactants can also be omitted completely, if desired.
The most important requirements of emulsification equipment are usually adequate and in particular variable emulsification power, sufficient shear or impact forces, fitting-out for uniform treatment of the batch, vacuum device, heating and cooling (14). These problems can be solved in a simple manner in accordance with the invention through the use of suitable micromixers, which ensure specific input of energy in each volume element and in which intensive mixing takes place in the thin channels with exposure to intensive shear forces.
The use of micromixers furthermore enables very small amounts of the desired cosmetic or pharmaceutical formulations to be prepared immediately before use. This has the advantage that the addition of emulsifiers, suspension aids and dispersion aids in the form of surfactants and other additives, such as, for example, stabilisers, can be greatly restricted or their use can be omitted entirely. It is also possible in this way for active ingredients or additives which are incompatible with one another in a formulation over an extended period not to be mixed with one another until directly before use.
Active ingredients which are only stable in a formulation in the form of a derivative can be initially introduced as such in a separate formulation and not added to the remaining mixture until directly before use. This also enables the user to add various additives, as desired, to small amounts of a base mixture at various points in time. This may be of interest both for pharmaceutical and for cosmetic formulations if different active ingredients are to be applied at different points in time.
Different additives can be added to a cosmetic base formulation for the day than for the night. Additives for the day may be, for example, UV filters, while those for the night may be regenerating additives.
For better understanding and for illustration, examples are given below which fall within the scope of protection of the present invention, but are not suitable for restricting the invention to these examples.